The intraspecific variability of mitochondrial genes of Agaricus bisporus reveals an extensive group I intron mobility combined with low nucleotide substitution rates

International audienceIntraspecific mitochondrial variability was studied in ten strains of A. bisporus var. bisporus, in a strain representative of A. bisporus var. eurotetrasporus and in a strain of the closely related species Agaricus devoniensis. In A. bisporus, the cox1 gene is the richest in group I introns harboring homing endonuclease genes (heg). This study led to identify group I introns as the main source of cox1 gene polymorphism. Among the studied introns, two groups were distinguished according to the heg they contained. One group harbored heg maintained putatively functional. The other group was composed of eroded heg sequences that appeared to evolve toward their elimination. Low nucleotide substitution rates were found in both types of intronic sequences. This feature was also shared by all types of studied mitochondrial sequences, not only intronic but also genic and intergenic ones, when compared with nuclear sequences. Hence, the intraspecific evolution of A. bisporus mitochondrial genome appears characterized by both an important mobility (presence/absence) of large group I introns and by low nt substitution rates. This stringent conservation of mitochondrial sequences, when compared with their nuclear counterparts, appears irrespective of their apparent functionality and contrasts to what is widely accepted in fungal sequence evolution. This strengthens the usefulness of mtDNA sequences to get clues on intraspecific evolution

Horizontal transfer of entire genomes via mitochondrial fusion in the angiosperm Amborella

We report the complete mitochondrial genome sequence of the flowering plant Amborella trichopoda. This enormous, 3.9 Mb genome contains six genome equivalents of foreign mitochondrial DNA, acquired from green algae, mosses, and other angiosperms. Many of these horizontal transfers were large, including acquisition of entire mitochondrial genomes from three green algae and one moss. We propose a fusion-compatibility model to explain these findings, with Amborella capturing whole mitochondria from diverse eukaryotes, followed by mitochondrial fusion (limited mechanistically to green plant mitochondria), and then genome recombination. Amborella?s epiphyte load, propensity to produce suckers from wounds, and low rate of mitochondrial DNA loss probably all contribute to the high level of foreign DNA in its mitochondrial genome.Fil: Rice, Danny W.. Indiana University. Department of Biology; Estados Unidos;Fil: Alverson, Andrew J.. Indiana University. Department of Biology; Estados Unidos;Fil: Richardson, Aaron O.. Indiana University. Department of Biology; Estados Unidos;Fil: Young, Gregory J.. Indiana University. Department of Biology; Estados Unidos;Fil: Sanchez Puerta, Maria Virginia. Consejo Nacional de Investigaciones Cientificas y Tecnicas. Centro Cientifico Tecnologico Mendoza. Instituto de Biologia Agricola de Mendoza; Argentina. Universidad Nacional de Cuyo. Facultad de Ciencias Exactas y Naturales. Departamento de Biologia; ArgentinaFil: Munzinger, Jérôme. Institut de Recherche pour le Développement (IRD). UMR Botanique et Bioinformatique de l’Architecture des Plantes (AMAP). Laboratoire de Botanique et d’Ecologie Végétale Appliquées; Nueva Caledonia;Fil: Barry, Kerrie. Department of Energy Joint Genome Institute; Estados Unidos;Fil: Boore, Jeffrey L.. Department of Energy Joint Genome Institute; Estados Unidos;Fil: Zhang, Yan. Penn State University. Department of Biology; Estados Unidos;Fil: dePamphilis, Claude W.. Penn State University. Department of Biology; Estados Unidos;Fil: Knox, Eric B.. Indiana University. Department of Biology; Estados Unidos;Fil: Palmer, Jeffrey D.. Indiana University. Department of Biology; Estados Unidos